1. Field of the Invention
The present invention relates generally to processes and microdevices for the injection of liquids and, more particularly, to processes, structures and materials for the construction and use of devices for the injection of fluids into the body, or in injection of fluids such as lubricants into machinery.
2. Description of the Related Art
Micro-injection processes and processes, structures and materials for the construction and use of devices for the injection of fluids into the body, or in injection of fluids such as lubricants into machinery. With these processes a small device which is designed to provide a target, for example, printing paper, a human body, or a motor vehicle with a certain amount of a liquid phase of a substance, for example, ink, drug, or petroleum using the method in which a pulse of electric or thermal energy is applied to the above-mentioned liquid, changing the liquid's volume and thus supplying the liquid to a specific target.
Recent developments in electrical and electronic technology have led to rapid development of such micro-injection devices. These devices have applicability in a variety of applications, an a example being in ink-jet printing. Different from dot matrix printers, ink-jet printers are capable of printing with multiple colors and have advantages of reduced noise and enhanced printing quality. Ink-jet printers are currently gaining in popularity. Typically, an ink-jet printer includes a printer head with a plurality of nozzles each having a minute diameter. The printer head operates in response to application of electrical energy from an external source, heating the nozzles with the energy received, bubbling and expanding ink in the nozzles and spraying the ink onto a printing paper.
In one type of ink-jet printer head, the ink is driven from the ink chamber by an oscillating layer, which is a membrane separating the ink chamber from the chamber containing the working fluid. This type of inkjet printer head however, suffers from several problems. The oscillating layer, usually made of a uniform material such as nickel, undergoes considerable flexing in its operation. This causes strong tensile stress over the surface of the oscillating layer, and leads to tearing in the high stress regions. This tearing in turn can lead to folding of the oscillating layer, further degrading its performance. As a result, the oscillating layer can not respond to the vapor pressure changes in the working fluid chamber, and performance is greatly reduced.
Some examples of print heads of the contemporary art are shown, for example, in the following U.S. patents. U.S. Pat. No. 4,032,929, to Fischbeck et al., entitled High Density Linear Array Ink Jet Assembly shows an ink jet assembly with a flexible diaphragm driven by actuators. The diaphragm is notched to provide a hinge for the motion of the diaphragm. This diaphragm, or membrane, is not subjected to changes in temperature, however and would probably not be suitable for use in a thermal ink-jet print head. U.S. Pat. No. 4,480,259, to Kruger et al, entitled Ink Jet Printer with Bubble Driven Flexible Membrane has a flexible membrane that separates the ink chamber from the chamber containing the working fluid, and the membrane is driven by the expansion of the working fluid as the fluid is volatilized upon heating. It mentions a membrane of silicone rubber, which is subject to the tensile stresses described above. U.S. Pat. No. 5,684,519 to Matoba et al., entitled Ink Jet Head with Buckling Structure Body; describes an ink jet head with a plate that is mechanically buckled thereby pushing the ink. Such a plate is designed specifically for mechanical buckling, and is not designed to be driven by a working fluid in a thermal ink-jet print head. U.S. Pat. No. 5,666,141, to Matoba et al., entitled Ink Jet Head and a Method of Manufacturing Thereof describes an ink jet head with a plate which buckles upon electric heating, thereby driving the ink.describes an ink jet head with a plate that buckles upon heating to drive the ink. The plate described in this patent is designed to buckle with heat, providing the force which drives the ink, however, and the plate is not designed to be driven by the expansion of a working fluid. Moreover, the plate is not specifically designed to prevent stress to the plate. U.S. Pat. No. 5,719,604, to Inui et al., entitled Diaphragm Type Ink Jet Head Having a High Degree of Integration and a High Ink Discharge Efficiency also describes an ink jet head with a plate that buckles upon heating to drive the ink. The plate described in this patents is designed to buckle with heat, providing the force which drives the ink and the plate is not designed to be driven by the expansion of a working fluid. This plate is not specifically designed to prevent stress to the plate.
Based upon my observation of the art, I have discovered that what is needed, then, is an oscillating layer which is not susceptible to the stresses caused by flexing. Moreover, I have found that an improvement in the working response of the oscillating layer will also lead to improvement in performance of devices such as ink-jet print heads.